CODE ：
#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=4e4+10;
int a[N];
int d[N];
void solve(){
memset(d,0,sizeof d);
int n,k;
cin>>n>>k;
for(int i=1;i<=n;i++){
cin>>a[i];
}
for(int i=1;i<=n/2;i++){
int l=min(a[i],a[n-i+1])+1,r=max(a[i],a[n-i+1])+k;
d[1]+=1;
d[r+1]-=1;
d[2]+=2;
d[1]-=2;
d[r+1]+=2;
d[a[i]+a[n-i+1]]-=1;
d[a[i]+a[n-i+1]+1]+=1;
}
int ans=2*n;
for(int x=2 ;x<=2*k;x++){
d[x]=d[x-1]+d[x];
ans=min(ans,d[x]);
}
cout<<ans<<endl;
}
signed main(){
ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
int T;
cin>>T;
while(T--){
solve();
}
return 0;
}
着急$qwqw$